/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the Qt Solutions component.
**
** $QT_BEGIN_LICENSE:BSD$
** You may use this file under the terms of the BSD license as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
**     of its contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#include "qtlockedfile.h"

bool QtLockedFile::lock(LockMode mode, bool block) {
  if (!isOpen()) {
    qWarning("QtLockedFile::lock(): file is not opened");
    return false;
  }

  if (mode == NoLock) {
    return unlock();
  }

  if (mode == m_lock_mode) {
    return true;
  }

  if (m_lock_mode != NoLock) {
    unlock();
  }

  struct flock fl;

  fl.l_whence = SEEK_SET;

  fl.l_start = 0;

  fl.l_len = 0;

  fl.l_type = (mode == ReadLock) ? F_RDLCK : F_WRLCK;

  int cmd = block ? F_SETLKW : F_SETLK;
  int ret = fcntl(handle(), cmd, &fl);

  if (ret == -1) {
    if (errno != EINTR && errno != EAGAIN) {
      qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
    }

    return false;
  }

  m_lock_mode = mode;
  return true;
}

bool QtLockedFile::unlock() {
  if (!isOpen()) {
    qWarning("QtLockedFile::unlock(): file is not opened");
    return false;
  }

  if (!isLocked()) {
    return true;
  }

  struct flock fl;

  fl.l_whence = SEEK_SET;

  fl.l_start = 0;

  fl.l_len = 0;

  fl.l_type = F_UNLCK;

  int ret = fcntl(handle(), F_SETLKW, &fl);

  if (ret == -1) {
    qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
    return false;
  }

  m_lock_mode = NoLock;
  return true;
}

QtLockedFile::~QtLockedFile() {
  if (isOpen()) {
    unlock();
  }
}
